In the medical field, a catheter which can be inserted into a lesion area along a biological lumen, for example, blood vessels, bile ducts, trachea, esophagus, or urethra in order to treat the lesion area generated in the biological lumen has been used. In general, the catheter is introduced into a biological lumen from an approach site which is formed by puncturing a living body. An introducer sheath which internally has a lumen is disposed on the approach site, and a catheter is introduced into a biological lumen through this introducer sheath. Accordingly, it is possible to insert a catheter into a biological lumen without directly causing friction between the catheter and biological tissues when treating a lesion area.
In recent years, the method of treating a lesion area in a biological lumen has become complicated. For example, in some cases, when treating chronic total occlusion (CTO) occurring in a blood vessel or the like, two catheters are simultaneously inserted into the blood vessel from both sides of the lesion area to treat the lesion area by the combined operation of the two catheters. At this time, it is necessary to form approach sites by puncturing two sites in order to insert the two catheters into the blood vessel and this has become a great burden on a person to be treated.
For example, JP-A-1-94863 discloses a catheter introducer for simultaneously inserting a plurality of catheters into a biological lumen from one approach site. The catheter introducer has one introducer sheath and a plurality of hubs which communicate with a lumen of the introducer sheath through an introduction passage. Accordingly, a plurality of catheters which have been respectively inserted into the plurality of hubs are guided into the one introducer sheath and are introduced into a biological lumen through the lumen in the introducer sheath. For this reason, only one approach site is formed in a person to be treated, and therefore, it is possible to reduce the burden on the person to be treated.
However, the lumen of the introducer sheath is formed to have a size that allows simultaneous insertion of a plurality of catheters, and therefore, it is also necessary to form the outer peripheral portion of the introducer sheath to be large in accordance with the size of the lumen. For this reason, even when using a small number of catheters with respect to the number of catheters which can be inserted into the introducer sheath, and for example, even when using only one catheter, the outer peripheral portion of the introducer sheath has the same size as that when using the set number of catheters. An approach site which is formed in a person to be treated through puncturing is formed in accordance with the size of this introducer sheath. Thus, even when using a small number of catheters, it is necessary to form the approach site having the same size as that when using the set number of catheters. Therefore, there is a disadvantage in that the size of the approach site is formed to be unnecessarily large.